php：//输出和内存使用情况

so I'm doing this in order to print out a csv file:

 while(ob_end_clean());
 $fp = fopen('php://output', 'w');
 fputcsv($fp, $header_fields);
  foreach($j as $fields){
    $row = array();
    foreach ($fields as $field){
      $row[] = $r->$field;
    }
    //stream each row
    fputcsv($fp, $row);
  }
  fclose($fp);
  exit;

My question is, suppose the csv will contain over 100,000 rows, will this cause an out of memory error or does this utilize the memory efficiently?